1. Field of the Invention
This invention relates to a rectangular waveform signal reproducing circuit for electronic musical instruments, and more particularly to such a rectangular waveform signal reproducing circuit which reproduces from a monophonic signal a rectangular waveform signal having its fundamental period.
Heretofore, a sound display of a monophonic signal from a monophonic electronic musical instrument by playing it is provided without processing the signal. Further, there has also been employed such a method which provides a sound display of the monophonic signal after processing it.
By reproducing from the monophonic signal a rectangular waveform signal having its fundamental period which varies as playing of the musical instrument proceeds, then gating the monophonic signal with the rectangular waveform signal and then applying the gated signal to a tone filter, a processed monophonic signal can be obtained. With a sound display based on the processed monophonic signal obtained as described above, a solo melody sound can be produced which is different from that obtainable with a sound display of the non-processed monophonic signal. Further, by frequency dividing the rectangular waveform signal, then gating the monophonic signal with the frequency-divided rectangular signal and then applying the gated signal to a tone filter, another processed monophonic signal can be obtained. The signal thus obtained produces a sound display which differs in pitch from that of the abovesaid processed monophonic signal.
Moreover, by converting the rectangular waveform signal reproduced from the monophonic signal into a DC signal having a voltage corresponding to its frequency and then applying the DC signal to a musical synthesizer, a sound signal having a desired pitch or tone can be obtained and, further, signals that the envelope and amplitude of the abovesaid signal are respectively modulated can be obtained.
This invention concerns a rectangular waveform signal reproducing circuit for electronic musical instruments which reproduces from a monophonic signal a rectangular waveform signal having the fundamental period of the monophonic signal which can be used for the abovesaid purpose.
2. Description of the Prior Art
In reproducing from a monophonic signal a rectangular waveform signal having its fundamental frequency, difficulties arise from the facts that the monophonic signal has a waveform containing high harmonic waves superimposed on the fundamental wave, that the period and amplitude of the fundamental wave vary as playing of an electronic musical instrument proceeds and that the amplitudes of the high harmonics also change as playing of the electronic musical instrument proceeds.
An attempt has heretofore been made to reproduce from the monophonic signal the rectangular waveform signal having its fundamental period. Owing to the abovesaid difficulties, however, such a rectangular waveform signal cannot be obtained unless the circuit for reproducing such a rectangular waveform signal becomes complicated and bulky or unless the rectangular waveform signal is trimmed by undesirable pulses.